The embodiments described and illustrated for exemplary purposes in international patent application published with No. WO-A-0016056, filed by the same applicant of the present patent application, include the above features.
In the hard disk memorizing units of electronic processors, generally the hard disk is a structure including a certain number of magnetic disks, aligned on a rotating spindle, capable of memorizing information in sectors arranged on concentric paths on both sides.
Read/write devices include magnetic heads carried by supports that enable all the heads to simultaneously cooperate with their associated disk surfaces.
More specifically, each head is coupled to a slider which is in turn coupled to a gimbal located at the end of a suspension arm. All the suspension arms are coupled, at their coupling ends opposite those carrying the magnetic heads, to an E-block actuator that includes a number of reciprocally parallel wings, typically exceeding by one the number of magnetic disks of the hard disk. The assembly consisting of the E-block actuator and of the suspension arms carrying the magnetic heads is commonly referred to as an HSA (“head stack assembly”).
In the course of the read/write operations in the memorizing unit, electric motors cause a rotational displacement of the HSA that displaces the magnetic heads towards their associated disk surfaces and the subsequent axial rotations of the spindle carrying the disks. The rotation of the hard disk and the specific shape of the sliders carrying the heads determine that between the disks and the sliders there be generated air bearings that urge the magnetic heads away from their associated disk surfaces. The thrust of the air bearings is counteracted by the force (“gram load”) applied by the suspension arms, that contributes to defining the flying height of the slider, in other terms, the distance between the slider and the surface of the magnetic disk in the course of the rotation of the latter. The typical flying height values in the present day units are within the range from 25 to 50 nanometers.
For the purpose of correctly accomplishing the read/write operations on the hard disk, the maintaining of a flying height at a pre-set and substantially constant value is a particularly critical aspect of the memorizing unit. Thus, the gram load value, that can vary, typically in the range from 1 to 5 grams with tolerances in the order of a few tenths of a gram, must be defined and checked with great attention.
The embodiments described and illustrated in the herein mentioned patent application published with No. WO-A-0016056 foresee thrust devices with levers including flat rest surfaces that cooperate with their associated thin plates by contacting the sliders carrying the magnetic heads. The sliding of each slider on its associated rest surface, in the course of the horizontal displacements of the lever, may damage the magnetic head carried by the slider, or in any case wear out the slider, even if the involved forces are extremely small.
Furthermore, these embodiments disclose the indirect detecting of height values of the slider by checking the position of the end of the lever that is in contact with the slider. Although this method may be in general accurate and reliable, it does not enable to check in a direct way the actual position of the slider, and may provide incorrect results in the event, for example, foreign matter were to deposit between the slider and the lever rest surface.